Power saws

ABSTRACT

Power saws and features for power saws are disclosed. Various features are particularly relevant to jobsite or benchtop table saws, such as a trunnion formed from a shaped tube, an elevation carriage, and an arbor block retention mechanism. Other features are particularly relevant to table saws, hand-held circular saws, track saws, miter saws, and band saws with active injury mitigation technology, such as an electrically isolating gear and an overmolded arbor/gear element.

This application is a continuation of U.S. patent application Ser. No.15/988,907, filed May 24, 2018, which claims the benefit of and priorityfrom U.S. Provisional Patent Application Ser. No. 62/511,234, filed May25, 2017, both of which are incorporated herein by reference.

FIELD

The present disclosure relates to power saws and features that may beimplemented in power saws. Various disclosed features are particularlyrelevant to portable table saws sometimes called jobsite or benchtopsaws. Various other disclosed features are particularly relevant totable saws, hand-held circular saws, track saws, miter saws, and bandsaws with active injury mitigation technology.

BACKGROUND

A power saw is a tool used to cut a workpiece, such as a piece of wood,to a desired size or shape. Table saws, hand-held circular saws, tracksaws, miter saws, and band saws are examples of power saws. A table sawincludes a work surface or table and a circular blade extending upthrough the table. A person uses a table saw by placing a workpiece onthe table and feeding it into contact with the spinning blade to cut theworkpiece to a desired size. A hand-held circular saw includes acircular blade, motor and handle. A person uses a hand-held circular sawby grasping the handle and moving the spinning blade into contact with aworkpiece. A track saw is similar to a hand-held circular saw, andincludes a track to guide the movement of the saw as the blade cuts theworkpiece. A miter saw includes a circular blade on a moveable supportarm. A person uses a miter saw by placing a workpiece under the bladeand then moving the blade into contact with the workpiece to make a cut,typically by pivoting the blade and support arm down. A band sawincludes a work surface and an adjacent band blade driven around two ormore rollers or wheels. A person uses a band saw by placing a workpieceon the work surface and moving the workpiece into contact with the bandblade.

Power saws are some of the most basic and versatile machines used inwoodworking and construction. For example, power saws are used in makingfurniture and cabinetry, in the installation of hardwood flooring, incutting plywood panels for roofing and walls, in cutting material forcountertops, in making pallets and crates, and for many other projectsand tasks.

Each type of power saw comes in various sizes and configurations. Forexample, table saws come in sizes ranging from large, stationary,industrial table saws, to small, lightweight, portable table saws.Larger table saws are sometimes called cabinet saws, mid-sized tablesaws are sometimes called contractor saws or hybrid saws, and smallertable saws are sometimes called portable, jobsite, or benchtop tablesaws. The larger table saws include induction motors and cast-ironparts, and typically weigh well over 100 pounds. The smaller, portabletable saws are often small and light enough to be transported in theback of a pickup truck, and they often have stands with wheels so theycan be moved around a jobsite or workspace. The smaller table saws haveuniversal motors and weigh less than 100 pounds. For example, jobsitesaws weigh approximately 60 to 80 pounds, and the smallest benchtop sawsweigh approximately 40 to 45 pounds.

Hand-held circular saws, track saws, miter saws and band saws also comein various sizes and configurations, and they can be equipped withdifferent features.

The names “table saws,” “hand-held circular saws,” “track saws,” “mitersaws,” and “band saws” are general categories that can overlap. Forexample, a track saw is a type of hand-held circular saw and can bereferred to as a hand-held circular saw. Miter saws and band saws havetables or work surfaces on which a workpiece is placed to make a cut,and in that regard are similar to a table saw. Nevertheless, thedesignations “table saws,” “hand-held circular saws,” “track saws,”“miter saws,” and “band saws” are generally understood by persons ofordinary skill in the art of woodworking and construction to identifydifferent categories or types of power saws.

Power saws present potential dangers or hazards because of the movingblade. Numerous accidents occur where a person using a power sawaccidentally comes into contact with the moving blade. To address thisissue, power saws can be equipped with active injury mitigationtechnology. Active injury mitigation technology detects a dangerouscondition, such as accidental contact with the moving blade by a person,and then performs some action to mitigate injury, such as stopping orretracting the blade in milliseconds. Generally, an embodiment of activeinjury mitigation technology includes at least a detection system todetect the dangerous condition and a reaction system to perform theaction to mitigate injury. An embodiment of active injury mitigationtechnology might also include a control system to control and/or testoperation of the detection and reaction systems. The terms “detectionsystem,” “reaction system” and “control system” are used to identifyknown categories of structural components, and therefore, identifystructure rather than function, just as the terms “actuator” and“sensor” identify known categories of structural components. Forexample, the term “detection system” is known to describe structuralelements such as electronic circuitry to generate and monitor anelectrical signal. The term “reaction system” is known to describestructural elements such as brake mechanisms and retraction mechanisms.The term “control system” is known to describe structural elements suchas electronic circuitry and controllers used to manage, control and/ortest the operability of the detection and reaction systems. U.S. patentapplication Ser. No. 10/100,211, filed Mar. 13, 2002 and titled “SafetySystems for Power Equipment,” which issued as U.S. Pat. No. 9,724,840 onAug. 8, 2017, describes active injury mitigation technology and variousimplementations and embodiments of active injury mitigation technologyin power saws. The entire disclosure of U.S. patent application Ser. No.10/100,211, and the patent resulting from that application, areincorporated herein by reference.

This document describes power saws and features that may be implementedin various categories of power saws. Some of the features described areparticularly relevant to portable table saws such as jobsite andbenchtop table saws. Other features described are particularly relevantto power saws with active injury mitigation technology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a portable table saw.

FIG. 2 shows an internal side view of the table saw of FIG. 1 with thehousing removed.

FIG. 3 shows an isometric view of the top of the table of the table sawin FIG. 1 isolated.

FIG. 4 shows an isometric view of the bottom of the table of FIG. 3.

FIG. 5 shows the housing of the table saw of FIG. 1 isolated.

FIG. 6 shows the bottom component of the housing of the table saw ofFIG. 1 isolated.

FIG. 7 shows the table insert and accompanying hold-down mechanism ofthe table saw of FIG. 1 isolated.

FIG. 8 shows an isometric bottom view of the hold-down mechanism of FIG.7 isolated.

FIG. 9 shows an isometric top view of the hold-down mechanism of FIG. 7isolated.

FIG. 10 shows a detail view of the table insert and hold-down mechanisminstalled in the table saw of FIG. 1.

FIG. 11 shows the fence of FIG. 1 isolated.

FIG. 12 shows a detail view of the portion of the table comprising afront rail.

FIG. 13 shows a detail view of the portion of the table comprising arear rail.

FIG. 14 shows a side view of the table saw of FIG. 1.

FIG. 15 shows the wrench mounting apparatus of FIG. 14 isolated.

FIG. 16 shows the arbor nut wrench of FIG. 14 isolated.

FIG. 17 shows the arbor flange wrench of FIG. 14 isolated.

FIG. 18 shows a front view of the table saw of FIG. 1.

FIG. 19 shows the trunnion of FIG. 2 isolated.

FIG. 20 shows the internal structure of FIG. 2 with some componentsremoved.

FIG. 21 shows a detail view of the front connection between the tableand trunnion.

FIG. 22 shows another view of the front connection between the table andtrunnion, with the table removed for clarity.

FIG. 23 shows a rear view of a front trunnion mounting plate isolated.

FIG. 24 shows a front view of the front trunnion mounting plate of FIG.23 isolated.

FIG. 25 shows a front view of a front trunnion bracket with somecomponents installed thereon.

FIG. 26 shows a rear view of the front trunnion bracket of FIG. 25 withsome components installed thereon.

FIG. 27 shows a front view of a rear trunnion bracket with somecomponents installed thereon.

FIG. 28 shows a rear view of the rear trunnion bracket of FIG. 27 withsome components installed thereon.

FIG. 29 shows a detail view of the rear trunnion connection to thetable.

FIG. 30 shows another detail view of the rear trunnion connection to thetable, with the table removed for clarity.

FIG. 31 shows a rear view of a rear trunnion mounting plate isolated.

FIG. 32 shows a front view of the rear trunnion mounting plate of FIG.31 isolated.

FIG. 33 shows a detail view of part of the elevation mechanism of thetable saw of FIG. 1.

FIG. 34 shows the bevel gear bracket of FIG. 33 isolated.

FIG. 35 shows the elevation shaft bracket of FIG. 2 isolated.

FIG. 36 shows another view of the elevation shaft bracket of FIG. 2isolated.

FIG. 37 shows a side view of the internal structure of the table saw ofFIG. 1 with some components removed for clarity.

FIG. 38 shows an isometric front view of an elevation carriage isolated.

FIG. 39 shows an isometric rear view of the elevation carriage of FIG.38 isolated.

FIG. 40 shows a brake cartridge bracket isolated.

FIG. 41 shows the brake cartridge bracket of FIG. 40 with somecomponents installed thereon.

FIG. 42 shows a brake cartridge cable housing and brake cartridgealignment bracket isolated.

FIG. 43 shows another view of the brake cartridge cable housing of thetable saw of FIG. 42 isolated.

FIG. 44 shows an elevation carriage with a brake cartridge bracket and abrake cartridge.

FIG. 45 shows a retraction bracket isolated.

FIG. 46 shows an alignment bracket isolated.

FIG. 47 shows a retraction bracket and elevation carriage with someadditional components installed thereon.

FIG. 48 shows a retraction bracket and elevation carriage with someadditional components installed thereon.

FIG. 49 shows a motor, gearbox, and alignment block isolated.

FIG. 50 shows another view of the motor, gearbox, and alignment block ofFIG. 49 isolated.

FIG. 51 shows an isometric top view of the alignment block in FIG. 49isolated.

FIG. 52 shows a side isometric view of the alignment block in FIG. 49isolated.

FIG. 53 shows a bottom isometric view of the alignment block in FIG. 49isolated.

FIG. 54 shows a detail view of part of the gearbox of FIG. 49.

FIG. 55 shows a detail view of the alignment block of FIG. 49 attachedto the gearbox of FIG. 49.

FIG. 56 shows some of the internal components of the motor and gearboxof FIG. 49 isolated.

FIG. 57 shows a perspective view of FIG. 56.

FIG. 58 shows a perspective view of an insulating gear.

FIG. 59 shows a side view of the gear of FIG. 58.

FIG. 60 shows a cross-sectional view of the gear of FIG. 58.

FIG. 61 shows another cross-sectional view of the gear of FIG. 58 in ahousing.

FIG. 62 shows part of the tilt mechanism of the table saw of FIG. 1 withsome components removed for clarity.

FIG. 63 shows the tilt plate of FIG. 62 isolated.

FIG. 64 shows the tilt lock lever and elevation shaft bracket of thetilt mechanism of FIG. 62 isolated.

FIG. 65 shows a cross-sectional view of the tilt lock lever andelevation shaft bracket of FIG. 64, taken along the line F-F in FIG. 64,with a tilt plate added.

FIG. 66 shows an alternative table insert and accompanying hold-downmechanism.

FIG. 67 shows an isometric bottom view of the hold-down mechanism ofFIG. 66 isolated.

FIG. 68 shows a perspective top view of the hold-down mechanism of FIG.66 isolated.

FIG. 69 shows a front view of the hold-down mechanism of FIG. 66isolated.

FIG. 70 shows a cross-sectional side view of the hold-down mechanism ofFIG. 66 isolated, taken along the line A-A in FIG. 69.

FIG. 71 shows a detail view of the table insert and hold-down mechanismof FIG. 66 installed in the table saw of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 shows a table saw 10. The table saw includes a table 12 with anopening 14 and an insert 16 in the opening. A blade 18 extends upthrough a slot 20 in the insert. A housing 22 supports the table and amotor is within the housing. The motor 200, shown in FIG. 2, is operablyconnected to the blade to drive or spin the blade. To use the table saw,a user places a workpiece on the table and slides it into contact withthe spinning blade to make a cut.

Table saws such as saw 10 can be equipped with “active injury mitigationtechnology.” That phrase refers to technology that detects a dangerouscondition, such as contact between a person and the spinning blade, andthen performs some predetermined action to mitigate any injury, such asstopping and/or retracting the blade. Exemplary implementations ofactive injury mitigation technology are described in InternationalPatent Application Publication No. WO 01/26064 A2, in U.S. patentapplication Ser. No. 10/100,211, filed Mar. 13, 2002, titled “SafetySystems for Power Equipment,” and in U.S. Pat. No. 9,724,840, issuingfrom U.S. patent application Ser. No. 10/100,211, all of which areincorporated herein by reference.

The blade in a table saw is typically supported in such a way that auser can change the elevation and tilt of the blade relative to the worksurface or table to cut material of various thicknesses and to makeangled cuts. FIG. 2 is an internal side view of table saw 10 withhousing 22 and other structures removed. FIG. 2 shows blade 18 supportedby an elevation carriage 30, which in turn is supported by a trunnion 32hanging from table 12. The elevation carriage moves up and down relativeto the trunnion to change the elevation of the blade relative to thetable, or relative to the work surface on the table, and the elevationcarriage and trunnion tilt or pivot from side to side to change theangle of the blade relative to the table or work surface.

In some table saws, the elevation of the blade is changed by turning ahand wheel, such as hand wheel 34 in FIG. 1. Typically, the hand wheelis connected to a shaft which turns bevel gears to raise and lower theelevation carriage as shown in FIG. 2, or alternatively, the hand wheelturns a screw that pivots the elevation carriage up and down. Othertable saws use a lever or other mechanism to raise and lower the blade.Tilting the blade is accomplished in some table saws by turning a secondhand wheel or a lever, and in other table saws by releasing a clamp andmoving the elevation hand wheel to the side, as shown in FIG. 2. Thespecific elevation and tilt mechanisms shown in FIG. 2 are discussed inmore detail below.

Table 12 is shown isolated in FIGS. 3 and 4. The table is made from diecast aluminum with ribs on the bottom side, shown in FIG. 4, to addstrength and rigidity while minimizing weight and manufacturing costs.It will be appreciated that table 12 could be made from other materialsor by other methods. Table 12 has two extensions 50 which allow a fence38 to have an increased lateral range, thus increasing the saw's ripcapacity, while keeping the saw lightweight.

Housing 22 includes a main body 52 and a base 54 attached to the mainbody (shown in FIGS. 5 and 6, respectively). The base is formed withribs and openings in what may be thought of as a honeycomb pattern. Theribs are close enough to prevent a user from reaching into the interiorof the saw, and the openings between the ribs allow sawdust to fallthrough. The height and size of different ribs can be varied to provideclearance for internal components of the saw. In the depictedembodiment, the base is injection molded out of plastic, although itwill be appreciated that other materials and methods could be used.

Base 54 can be joined to the main body 52 to form housing 22 in variousways. In the depicted embodiment, the base is screwed to the main body,and the base and main body include screw holes and bosses for thescrews. Main body 52 can also include sockets that can be used to clampor mount the saw to a cart, stand, or benchtop, such as sockets 56 shownin FIG. 5.

Inserts used in table saws typically lock in place in the blade openingso that the blade does not kick the insert back toward the user if theblade contacts the insert. Locking the insert into place also preventsthe insert from popping up and presenting an edge that might catch aworkpiece as the workpiece moves toward the blade. In saws with activeinjury mitigation systems, particularly those in which the systemmonitors an electrical signal for changes indicative of contact betweena user and the blade, the throat plate is typically made of, or coatedwith, non-conductive material.

An insert fits into an opening in a table. The opening is sometimescalled a “throat” or “blade opening” and the insert is sometimes calleda “throat plate.” The opening is typically large enough for a user toperform some types of service or maintenance to the saw through theopening, such as changing the blade. An opening in the table around theblade, however, means the table cannot support a workpiece next to theblade, so the insert is placed in the opening around the blade tosupport a workpiece adjacent the blade. As seen in FIG. 1, insert 16fits in opening 14 in table 12. The insert includes a slot or channel 20through which the blade extends. The insert is removable so a user canaccess internal components of the saw through the blade opening (forexample, a user can remove the insert to change the blade, to access themount for a riving knife or spreader, or to change out a cartridge usedin an active injury mitigation system). In the depicted exemplaryembodiment, insert 16 and corresponding opening 14 are generallyrectangular in shape. This allows the throat plate opening to extendcloser to the edges of the table, thus increasing the capacity of thehole and the accessibility of the internal components of the saw.

Opening 14 has eight support tabs, or ledges, 28, which are shown inFIGS. 3 and 4. The support tabs 28 extend a short way into opening 14from the underside of the table, and support insert 16 when the insertis placed within the opening. The rear of the insert can be held downand/or locked into place in many ways. In the depicted embodiment, tabs112 (labeled in FIG. 7) extend from the rear of insert 16 and fit undera corresponding ledge on table 12. The front of insert 16 is held inplace by a sliding lock member actuated by a lever or tab.

FIGS. 7 through 10 show a mechanism to hold down the front of an insertthat is simple to operate and that does not require a tool to install,lock, unlock, or remove. FIG. 7 shows the top of insert 16 with thehold-down mechanism installed therein. The insert includes an opening orindentation 110 sized to accommodate both the hold-down mechanism and auser's finger. In the depicted embodiment, a finger lever 114 isconfigured to be pulled toward the front of the saw to release theinsert from the blade opening because pulling the lever in thatdirection is a convenient, intuitive movement when a finger is insertedinto indentation 110. Finger lever 114 is shown actuated (angled up) inFIG. 7, and un-actuated (generally horizontal) in FIGS. 8, 9, and 10. Anadditional benefit of the configuration of finger lever 114 is that,should a user forget to press the lever back down to lock the insert inplace, a piece of wood or other material to be cut would pass acrossfinger lever 114 and push it down into the un-actuated, locked position.

FIGS. 8 and 9 show the hold-down mechanism isolated from insert 16.Finger lever 114 bends down and becomes lock lever 116, and a dowelportion 118 is interposed between lever portions 114 and 116. Lock lever116 fits into a generally rectangular opening 122 in lock block 120.Lock block 120 is connected to the bottom of insert 16 by a screw 128,which passes through a washer 130 and into a portion of insert 16 whichextends down into elongated opening 124 in lock block 120, as shown inFIGS. 8, 9, and 10. The downward extension of insert 16 allows fortranslation of lock block 120 in the forward and backward directions,but not sideways or vertically.

Dowel portion 118 fits within two sets of projections 132 extending downfrom insert 16, which allow dowel portion 118 to pivot, but not moveforward, backward, or up. When finger lever 114 is pushed down intoindentation 110, dowel portion 118 pivots within projections 132. Thiscauses lock lever 116 to push lock block 120 towards the front of thesaw until front edge 126 of said lock block 120 overlaps with acorresponding ledge on table 12, as shown in FIG. 10. This prevents thefront of insert 16 from rising up during use. In order to remove theinsert, a user would place a finger into indentation 110 and pull fingerlever 114 up toward the front of the saw. This would cause front edge126 to retract and cease to be in contact with table 12. The user couldthen lift the front of insert 16 out of opening 14, slide tabs 112 outof contact with the table and remove the insert from opening 14.

As shown in FIG. 7, insert 16 has a slot 20, shown in dashed lines, thatruns from a wider opening 134 at the rear of the insert to near thefront. The insert depicted in FIG. 7 is a zero-clearance insert, so slot20 is cut by the blade, as is known in the art. Slot 20 connects withopening 134 at the rear of the slot (the rear of the slot is the portionof the slot furthest away from the front of the table saw when theinsert is in the blade opening). Opening 134 allows room for a rivingknife 36 or splitter to extend up through the insert, as shown in FIG.1.

Inserts as described herein, when used in a saw having active injurymitigation technology, can be made of phenolic or wood. Both materialsare non-conductive, which is preferable for active injury mitigationssystems, but are relatively expensive. In the presently disclosedembodiment, insert 16 is made entirely from plastic. Alternatively, theinsert could be made out of metal overmolded with plastic, but such aninsert would involve extra manufacturing steps.

In an alternate exemplary embodiment, insert 16 could include screws orother features to level the insert in the blade opening and to adjustthe insert so that the top surface of the insert is substantiallycoplanar with the top of table 12, as described in U.S. PatentApplication Publication No. 2015-0107430, titled “Inserts for TableSaws,” published Apr. 23, 2015 and issuing as U.S. Pat. No. 9,919,369 onMar. 20, 2018, which is incorporated herein by reference.

A blade guard, spreader, and/or riving knife may be positioned adjacentthe rear edge of the blade to shield the blade and/or to prevent aworkpiece from catching the rear of the blade. FIG. 1 shows a rivingknife 36, which is supported by elevation carriage 30. Riving knife 36raises, lowers and tilts with elevation carriage 30, and therefore,maintains a constant position relative to the blade. Various mechanismsfor mounting a blade guard, spreader, and/or riving knife to anelevation carriage in a table saw are described in U.S. PatentApplication Publication No. 2015-0107427-A1, published Apr. 23, 2015,which is incorporated herein by reference.

Often, a user of a table saw guides a workpiece past the blade with afence, such as fence 38 in FIG. 1, which is shown isolated in FIG. 11.The fence mounts to the top of the table saw and provides a fixedreference surface relative to the blade. The user can slide theworkpiece against and along the fence to make a cut. The fence helpskeep the workpiece moving in a straight path without shifting orrotating, and therefore, helps produce a straight cut. The fence can besecured at various positions relative to the blade so that a workpiececan be cut to different dimensions. The fence clamps to an integrallyformed rail running along the front edge of table 12, such as front rail42 in FIG. 1, shown with fence 38 in FIG. 12, and the fence can belocked or clamped anywhere along the rail. The fence may also rest on orclamp to an integrally formed rail running along the rear of the table,such as rear rail 44 in FIG. 1, shown with fence 38 in FIG. 13. In analternate exemplary embodiment the front and rear rails 42 and 44 couldbe removable components, not integrally formed as part of the table.Various fences are described in U.S. Patent Application Publication No.2015-0107428-A1, titled “Fences for Table Saws,” published Apr. 23, 2015and issuing as U.S. Pat. No. 9,757,871 on Sep. 12, 2017, which isincorporated herein by reference.

The length of the rail portion of the table along the front of the sawdetermines how far the fence can be positioned from the blade, andtherefore, the largest dimension that can be cut on the saw using thefence. This may be called the cutting capacity or rip capacity of thesaw. Some table saws include rails sufficiently long to provide 36inches of cutting capacity—in other words, the face of the fence nearestthe blade is 36 inches away from the blade so a workpiece can be cut to36 inches wide. Other table saws include rails with 52 inches of cuttingcapacity. Saws with these cutting capacities are typically stationarysaws called cabinet saws or contractor saws. Smaller, portable saws,such as jobsite or benchtop saws, typically provide anywhere from 12inches to about 30 inches of cutting capacity. These smaller, portablesaws have shorter rails in order to minimize the size and weight of thesaw. In an alternate exemplary embodiment, the rails may move ortelescope out to provide increased cutting capacity.

Examples of front and rear rail portions 42 and 44 are shown with fence38 in FIGS. 12 and 13 respectively. The front rail portion is elongatewith a channel 60 extending along the front face of the rail. Thechannel helps guide the fence when a user slides the fence along therail. The channel also includes a ruler 62 that can be read by the userto facilitate positioning of the fence at a desired distance from theblade without having to use a separate tape measure. It can be seen inFIGS. 11 and 13 that fence 38 has an extension 40 which extends downfrom the back of the fence and then bends at a 90 degree angle towardsthe front of the saw to hook under the rear rail portion. When thehandle portion of fence 38 is generally parallel with the main body ofthe fence, extension 40 is pushed away from the main body of the fence.In this configuration, the fence is free to slide to the left or rightalong rails 42 and 44. When the user has moved fence 38 to the desiredposition, the user would push the handle portion down to the positionshown in FIGS. 11 and 12, which would clamp the fence to the front railand position the angled portion of extension 40 underneath rear rail 44.The handle portion of fence 38 also has an extension that fits underrail 42 to further hold the fence in place during use.

Table saw 10 also includes on-board storage for a pushstick 70, an arbornut wrench 72, and an arbor flange wrench 74, as shown in FIG. 14. Theright side of housing 22 has a portion which extends out to form a ledge76 with two sets of upwardly extending, U-shaped flanges, 78 and 80,which form a mounting system or structure to hold the pushstick 70. Theinside edge of the outer portion of each flange has a tab that fits overa beveled portion of the pushstick to hold the pushstick in place. In analternate exemplary embodiment, housing 22 could also be formed with twoor more generally T-shaped extensions around which a power cord could bewound. Saw housing 22 has a generally vertical, slightly recessed area82 under the ledge 76, configured to provide clearance for wrenches 72and 74 within the footprint of housing 22. A carriage bolt 84 passesthrough the recessed area to form a projection extending in a directionnormal to saw housing 22, as shown in FIG. 15. A washer 86 and extensioncomponent 88 are tightly threaded onto the screw such that washer 86abuts housing 22 and firmly secures bolt 84, as is shown in FIG. 15.FIGS. 16 and 17 show arbor wrenches 72 and 74, respectively. Arbor nutwrench 72 includes a socket 90 at one end configured to fit around anarbor nut, and a hole 92 sized to fit over extension 88 and the shaft ofbolt 84. Arbor nut wrench 72 also includes a tapered end 94 which can beused to help remove brake cartridges used in table saws with activeinjury mitigation systems. Said brake cartridges stop and/or retract theblade in the event of an accident and they must be removed after use.Occasionally, the act of stopping and/or retracting the blade causes thebrake cartridge to press tightly against its mount, and in thatsituation, arbor nut wrench 72 can be used as a lever to pry the brakecartridge off its mount. Arbor flange wrench 74 includes a generally Ushaped opening 96 configured to fit around an arbor shaft, and a hole 98sized to fit over extension 88 and the shaft of bolt 84. To store thewrenches on the side of the saw, a user would place the blade wrenchesonto the shaft of bolt 84 and slide them over extension 88. The userwould then place wing-nut shaped locking knob 100 on the shaft of bolt84 and turn said knob to secure the wrenches so they could not slide offthe extension and bolt. To remove the arbor wrenches, a user wouldsimply rotate the locking knob in the opposite direction until it couldbe removed from the shaft of bolt 84, and then the user could slide oneor both wrenches off of extension 88 and bolt 84.

Table saws are typically started and stopped by a user flipping ortriggering some type of switch on the saw. Such switches should bedesigned and positioned so they are easy and intuitive to use, but alsoso they are protected and so they can be repaired or replaced easily, ifnecessary. A switchbox having these characteristics is disclosed in USPatent Application Publication No. 2016-0243632, published Aug. 25,2016, titled “Table Saws,” which is herein incorporated by reference.FIG. 18 shows the position of switchbox 1000 in saw housing 22.

Switchbox 1000 switches power to a motor 200 shown in FIGS. 2, 49, and50. (FIG. 2 shows a left-side view of the internal mechanism of saw 10.)In the depicted embodiment, motor 200 is a direct drive universal motor.A gearbox 202 is attached to the motor and said gearbox is attached toelevation carriage 30. Elevation carriage 30 is a bent sheet metal part,shown isolated in FIGS. 38-39. In the depicted embodiment, an arborblock assembly is attached to elevation carriage 30 by bolts threadinginto sockets 720, 722 and 726 in the arbor block, as shown in FIGS. 49and 50. The elevation carriage, in turn, is supported by a trunnion,such as trunnion 32 shown in FIG. 2, in such a way that the elevationcarriage can raise and lower relative to the trunnion. The trunnion issupported by table 12 in such a manner that the trunnion can tiltrelative to the table. In the depicted embodiment the trunnion tilts tothe right when facing the front of the saw, but could be designed totilt to the left.

In many saws, the trunnion is a die cast aluminum part, but in thedepicted embodiment, trunnion 32, shown isolated in FIG. 19, is atorsion transfer member formed from a unitary piece of hollow steeltubing bent into a something similar to a U shape. This design isadvantageous because it reduces the cost and complexity ofmanufacturing.

Trunnion 32 is comprised of two generally parallel, generally verticalsections 302 and 304, connected to a bottom section 306, by corners 308and 310. Trunnion 32 has holes 312, 314, 316, 318, 320, 322, 324, 326,328, 330, 332, 334, 336, and 338, the uses of which will be discussedlater. While only one side of each hole is labeled in FIG. 19, each ofthe holes has an accompanying hole on the opposite side of the hollowtrunnion tube. Rear section 304 extends slightly further down relativeto front section 302, as seen in FIG. 2, so corner 310 has a slightlynarrower angle than corner 308 since the bottom section 306 slopes or isangled such that the back end is lower than the front end, relative totable 12. The rear end of bottom section 306 is lower to provideclearance for bevel gears 350 and 352 as well as to allow elevationcarriage 30 to be tall enough to provide stability in both the verticaland horizontal directions. This trunnion design has several advantages,including low cost, simplicity, and ease of manufacturing.

The trunnion 32 mounts to the table 12 via front and rear mountingplates 354 and 358, which are pivotally connected to respective frontand rear trunnion brackets 356 and 360. The trunnion, mounting plates,and brackets are shown in FIG. 20, with some other structures of the sawremoved for clarity. The front connection between the trunnion and tableis shown in FIGS. 21 and 22, the front trunnion mounting plate is shownisolated in FIGS. 23 and 24, and the front trunnion bracket is shownisolated in FIGS. 25 and 26. The rear trunnion bracket is shown isolatedin FIGS. 27 and 28, the rear connection between the trunnion and tableis shown in FIGS. 29 and 30, and the rear trunnion mounting plate isshown isolated in FIGS. 31 and 32.

Front trunnion mounting plate 354 is made from a unitary piece of bentsheet metal. FIG. 23 shows an isometric view of the back side of themounting plate, relative to the front of the saw, and FIG. 24 shows thefront side of the mounting plate. As shown in FIGS. 21 and 22, fronttrunnion mounting plate 354 mounts to trunnion 32 via three screws. Twoparallel screws 380 pass through holes 372 and 374 in front trunnionmounting plate 354 and then through holes 338 and 334 respectively intrunnion 32. It can be seen in FIG. 22 that the parallel screws 380 areflush with the front edge of front trunnion mounting plate 354. This isbecause holes 372 and 374 are countersunk on the front side of theplate, as shown in FIG. 24, and the angled surfaces provide space forthe heads of the screws. Each of the three screws used to attach fronttrunnion mounting plate 354 to trunnion 32 is held in place by a washerand hex nut, although it will be appreciated that other methods ofattaching components to the trunnion could be used. The third screw,382, passes through hole 378 in front trunnion mounting plate 354,through hole 336 in trunnion 32, and then through hole 376 in fronttrunnion mounting plate 354. Holes 376 and 378 are located on portionsof front trunnion mounting plate 354 which are bent such that they areperpendicular to the main section. Front trunnion mounting plate 354attaches to front trunnion bracket 356 via two screws 390, which passthrough holes 364 and 366 in front trunnion mounting plate 354. Fronttrunnion bracket 356 has an elongate, generally horizontally oriented,arcuate opening 400, through which screws 390 pass, as shown in FIGS. 25and 26. Between screws 390, there is an arcuate sliding piece 408,shaped to fit within, and slide along, arcuate opening 400, with holesfor screws 390 and depressions 414 and 416, which are designed toreceive cylindrical projections 368 and 370 on front trunnion mountingplate 354.

Front trunnion bracket 356 is shown with screws 390, washers 392, andsliding piece 408 in FIGS. 25 and 26. Sliding piece 408 can move withinarcuate opening 400 in order to allow the trunnion 32 and accompanyingblade, arbor, and motor, to tilt up to 45 degrees in order to allow auser to make angled cuts. Front trunnion bracket 356 is made from aunitary piece of sheet metal bent horizontally at an angle of about 90degrees about a third of the way up the piece. The horizontal third ofthe bracket has three holes 402, 404, and 406. Two screws 394 passthrough washers 396 and holes 402 and 406 in front trunnion bracket 356and attach to table 12, as shown in FIGS. 21 and 22. Eccentric roller398 passes through hole 404 in front trunnion bracket 356 and insertsinto a projection in table 12. It can be seen in FIG. 25 that holes 402and 406 are oblong, with the long sides parallel with the bend in thefront trunnion bracket 356. Hole 404 is also oblong, but is wider thanholes 402 and 406, and its long sides are perpendicular to the bend inthe front trunnion bracket 356. A user could rotate the eccentric roller398 in hole 404 in order to provide fine lateral adjustment for thetrunnion and therefore the blade and motor assembly relative to thetable. The front trunnion bracket is allowed to have slight lateralmovement with the rotation of eccentric roller 398 because holes 402 and406 can move relative to screws 394.

Rear trunnion bracket 360 is shown with screws 390, washers 392, andsliding piece 408 in FIGS. 27 and 28. Both front trunnion bracket 356and rear trunnion bracket 360 have identical arcuate openings 400,screws 390, washers 392, and sliding pieces 408. Rear trunnion bracket360 is made from a unitary piece of sheet metal bent horizontally at anangle of about 90 degrees about a third of the way up the piece. Twoscrews 426 pass through washers 428 and holes 430 and 432 in thehorizontal part of rear trunnion bracket 360 and attach to table 12, asshown in FIGS. 29 and 30. Holes 430 and 432 in rear trunnion bracket 360are, like holes 402 and 406 in front trunnion bracket 356, oblong toprovide lateral clearance for movement relative to screws 426 to allowfor lateral adjustment of the trunnion.

Rear trunnion bracket 360 attaches to rear trunnion mounting plate 358in the same manner in which front trunnion bracket 356 attaches to fronttrunnion mounting plate 354. Screws 390 pass through sliding piece 408and holes 446 and 452 in rear trunnion mounting plate 358 to secure reartrunnion mounting plate 358 to rear trunnion bracket 360. Cylindricalprojections 448 and 450 on rear trunnion mounting plate 358 are shapedto fit into corresponding cylindrical depressions 414, 416 in slidingpiece 408 to provide additional stabilization between the rear trunnionmounting plate 358 and rear trunnion bracket 360. This connection, aswell as the connection between the rear bracket and the table is shownin FIGS. 29 and 30.

Both front and rear trunnion brackets are installed in table saw 10 suchthat the horizontal sections used to attach the trunnion brackets to thebottom of table 12 both extend towards the front of the saw.

Rear trunnion mounting plate 358 is shown isolated in FIGS. 31 and 32.It is made from a unitary piece of sheet metal bent to fit around theback and over the top of the rear vertical component 304 of trunnion 32,as shown in FIGS. 29 and 30. Two parallel screws 458 pass through holes438 and 440 in rear trunnion mounting plate 358 and then through holes312 and 316 in trunnion 32. A third screw 460, which is perpendicular tothe two screws 458, passes through hole 442 in rear trunnion mountingplate 358 and hole 314 in trunnion 32. As with the front trunnionmounting plate, the three screws 458 and 460 are secured by washers andhex nuts.

It will be appreciated by those of ordinary skill in the art that foldedportions of sheet metal parts, such as the trunnion mounting plates,could be welded to another portion of the part in order to strengthenthe overall part. Examples of such welds are shown in FIG. 31 at 441,and in FIG. 32 at 443.

FIG. 33 shows a bevel gear bracket 470 attached to sections 304 and 306of trunnion 32 via two screws 486 and 488, which pass through holes 482and 484 in sections 472 and 478 of the bracket respectively, and holes318 and 320 in trunnion 32, respectively. Bevel gear bracket 470, shownisolated in FIG. 34, is generally shaped like a W with generally rightangles and is made from a single piece of bent sheet metal with sections472, 474, 476, 478, and 494. The two wing sections 494 extend towardseach other from generally vertical section 476 and generally horizontalsection 474 on one side of the bevel gear bracket. The wing sectionsprovide stability and rigidity to the bracket. It is advantageous toonly provide them on one side of the bevel gear bracket in order toallow for easy access to the bevel gears from the other side of thebracket.

Hand wheel 34 connects to an elevation control shaft 510, which passesthrough an arcuate opening 26 in saw housing 22, an elevation shaftbracket 512, hole 324 in trunnion 32, through hole 492 in bevel gearbracket 470, and terminates in a bevel gear 350, as shown FIGS. 2, 33and 37. FIGS. 35 and 36 show elevation shaft bracket 512 isolated fromother structures. Elevation shaft bracket 512 is formed from a generallyrectangular piece of sheet metal bent to fit around the front and sidesof front vertical section 302 of trunnion 32. It is attached to trunnion32 via two bolts 530, which pass through holes 516, 518, 520, and 522 inelevation shaft bracket 512 and holes 326 and 328 in trunnion 32, asshown in FIG. 37. When elevation shaft bracket 512 is viewed from thefront of saw 10, the front third is generally rectangular, with anupside-down U shape 528 pressed into it at an angle, such that thecurved part of the U is pressed further in to the metal. There is a hole526 in the curved part of the U shape 528, through which elevationcontrol shaft 510 passes, and the U shaped indentation 528 allows thehole 526 and elevation control shaft 510 to meet at a perpendicularangle. At the top of the front portion is an extension with a generallysquare hole 514 at the top through which a carriage bolt for a tilt locklever passes, as will be discussed later in more detail. The left thirdof the bracket has two holes, 516 and 518, and the bottom corner is cutaway at an angle of about 45 degrees, as shown in FIG. 36. The rightthird of the bracket has a horizontal cut approximately two thirds ofthe way down, with the top piece bent backwards parallel to the leftthird, and having two holes 520 and 522, which correspond with holes 516and 518 in the left third. The bottom portion of the right third of theelevation shaft bracket is parallel with the front third, and it has ahole 524 through which a screw passes to mount a bevel gauge 540, asshown in FIG. 18. The front face of the bottom portion of the rightthird is recessed slightly, so that the left edge of the bevel gauge 540meets the step between the face of the middle third and the bottomportion of the right third, which keeps the bevel gauge from rotatingaround the screw in hole 524.

The bevel gear 350 at the end of elevation control shaft 510 oppositehand wheel 34 is in operative contact with a bevel gear 352 at the baseof a threaded elevation shaft 300. This is shown in FIGS. 2, 20, 33, and37. Elevation shaft 300 is threaded at a shallow angle, and this designis advantageous because it forms a sort of anti-backdrive mechanism,since friction and the slope of the threads on shaft 300 keeps elevationcarriage 30 and its accompanying components from slipping or driftingdown unexpectedly. The bottom of the threaded elevation shaft passesthrough a hole 490 in the bevel gear bracket 470 and the top terminatesin a hole 444 in rear trunnion mounting plate 358 (labeled in FIG. 31).The top and bottom ends of the elevation shaft are not threaded.

Elevation carriage 30, shown isolated in FIGS. 38 and 39, is a piece ofsheet metal bent to fit around threaded elevation shaft 300. Twothreaded bushings 546 are non-rotatably mounted to the top and bottom ofthe elevation carriage 30, as shown in FIG. 48. As hand wheel 34 isrotated, it causes elevation control shaft 510 and bevel gear 350 torotate, and bevel gear 350 meshes with bevel gear 352 on threadedelevation shaft 300 and causes the elevation shaft to rotate, thuscausing the threaded bushings 546 and therefore elevation carriage 30 tomove up or down along the shaft. It is advantageous that the threadedbushings be spaced as far apart as possible vertically in order toprovide additional stability to prevent rotation of the motor and bladeout of plane with the elevation carriage 30 and threaded elevation shaft300.

Elevation carriage 30 is a single sheet metal piece, with a generallyrectangular rear section 554, and four sections 548, 550, 552, and 556extending in the same direction away from rear section 554 at an angleof about 90 degrees. Viewed from the front of the saw, rear section 554has two corners cut into its right side, relative to the front of thesaw. The part of rear section 554 left between the corners is bent at 90degrees and becomes section 556, to which the riving knife mount isattached via holes 576, 578, 580, 582, 584, 586, and 588, and acartridge bracket 600 is attached through hole 574, as will be discussedlater. On the opposite side, rear section 554 is folded at about 90degrees to become section 552, which is parallel to section 556. Hole574 in section 556 lines up with hole 570 in the opposite section 552. Apivot shaft 624 passes through holes 570 and 574, as shown in FIG. 48,and its purpose will be discussed later. The top of section 552 extendsaway from rear section 554 about half the distance of opposite section556, and then extends at a slight downward angle further away from rearsection 554 until it is longer than opposite section 556, beforeterminating in a nearly vertical surface and angling back towards rearsection 554. At the front end of section 552, relative to the front ofthe saw, is a metal detent projection or pin 592 and its role in theretraction of the motor and blade as part of the active injurymitigation system will be discussed later. A feature of the depictedembodiment is that metal detent pin 592 is formed by stamping elevationcarriage 30. In other words, in the depicted embodiment metal detent pin592 is a stamped projection. This decreases the manufacturing cost ofthe saw, since fewer parts are needed, and stamping sheet metal parts isa relatively simple process.

Above the metal detent pin 592 there is a threaded socket 572, thepurpose of which will also be discussed later. At the top and bottom ofsection 554 are two small tabs, 590, which fold over matching sections548 and 550. Tabs 590 serve to limit the vertical movement of elevationcarriage 30 and, therefore, prevent blade 18 from moving too far up ordown. The upper elevation limit is defined by rear trunnion mountingplate 358, and the lower elevation limit is defined by bevel gearbracket 470. In an alternate exemplary embodiment, tabs 590 couldinclude screws or other adjustment mechanisms to allow fine adjustmentof the vertical range of movement for elevation carriage 30. Thematching sections 548 and 550 are folded away from rear section 554 atabout 90 degrees, and are generally perpendicular to sections 552 and556, as shown in FIGS. 38 and 39. They have matching holes 558 and 564,respectively, through which threaded elevation shaft 300 passes. Holes560 and 562 in section 548 line up with holes 568 and 556, respectively,in section 550, and the threaded bushings 546 are attached to elevationcarriage 30 via screws passing through said holes.

Brake cartridge bracket 600, shown isolated in FIG. 40, is used tosupport a brake cartridge when table saw 10 includes an active injurymitigation system with a brake cartridge. It is pivotally attached tosection 556 of elevation carriage 30 via pivot shaft 624, which passesthrough hole 616 in brake cartridge bracket 600 and holes 570 and 574 inelevation carriage 30, as shown in FIGS. 41, 44 and 48. Brake cartridgebracket 600 is formed from a single piece of sheet metal with holes 602,604, 606, 608, 610, and 616. Hole 610 is shaped to allow a protrusion ofa plug or socket, such as that on brake cable board housing 634, to passthrough it, and it is shaped generally like a rectangle with the cornersremoved and it has a notch in the rear end (relative to the front of thesaw), through which a screw passes in order support a plug or socketthat connects to switchbox 1000. Additional support for brake cableboard housing 634 is provided by a second screw which passes throughhole 608 in brake cartridge bracket 600. A plastic positioning pin 632is attached to the brake cartridge bracket through hole 606, as shown inFIG. 41. The brake cartridge bracket and plug are positioned so thatbrake cartridge 630 automatically engages the plug when the brakecartridge is seated on shaft 624 and plastic positioning pin 632. Hole610 is slightly oversized to allow some play for brake cable boardhousing 634 to allow its D-Sub connector to contact the accompanyingD-Sub connector in brake cartridge 630.

In the depicted embodiment, pivot shaft 624, positioning pin 632, andbrake cartridge bracket 600 provide a single, fixed position for brakecartridge 630, as shown in at least FIG. 44. In some table saws, thesystem to mount a brake cartridge in the saw allows for the position ofthe brake to be adjusted so that the brake can be moved closer to orfurther from the edge of the blade. The depicted embodiment, incontrast, provides a stationary or fixed mount and the position of thebrake cannot be adjusted. This simplifies the design and reduces themanufacturing cost of the saw. This also simplifies the operation of thesaw because a user does not need to adjust the position of the brakecartridge relative to the blade. This also prevents a user frompositioning the brake cartridge further from the blade than it shouldbe, which might happen by mistake or inadvertence in a system where theposition of the brake cartridge was adjustable. The design and functionof brake cartridge 630 are described in detail in U.S. Pat. No.8,459,157, issued Jun. 11, 2013, which is herein incorporated byreference.

FIG. 42 shows a brake cable board housing 634 attached to the side ofbrake cartridge bracket 600 on the side opposite where brake cartridge630 attaches. Brake cable board housing 634 has a D-sub connector whichconnects with brake cartridge 630, and two cables 636 and 638. Cable 636contains wires relating to a Hall Effect sensor to monitor bladerotation, detection signal monitoring, and grounding. Cable 636 may alsoconnect to a conductive coupling used in some implementations of activeinjury mitigation technology. Conductive couplings for power tools withactive injury mitigation technology are described in PCT PatentApplication No. PCT/US17/34566, titled “Detection Systems for PowerTools with Active Injury Mitigation Technology,” filed on May 25, 2017,and naming Stephen F. Gass, John P. Nenadic and Louis R. Slamka asinventors, the disclosure of which is herein incorporated by reference.Cable 636 described above may correspond to cable or wire 274 in the PCTpatent application, and the discussion concerning cable or wire 274 inthe PCT application applies to cable 636 herein. Cable 638 connects tothe switchbox. Internal circuitry and/or programming related to activeinjury mitigation technology may be housed in the brake cartridge,and/or in brake cable board housing 634. In the depicted embodiment, itcan be advantageous to form the cable board housing from two parts thatmate with something like a tongue and groove connection in order tominimize dust permeability.

Retraction bracket 660, shown isolated in FIG. 45, is pivotally attachedto elevation carriage 30 via a bolt 676 which passes through pivot shaft624 and hole 666 in the retraction bracket, as shown in FIG. 47. Theretraction bracket can be thought of as shaped generally like a square,with a small ledge formed by bending the bottom edge out at an angle ofabout 90 degrees. The rear corner, relative to the front of the saw, isremoved, leaving a horizontal edge and a vertical edge connected by athird edge, which is angled at about 45 degrees, as seen in FIGS. 45 and47. The retraction bracket 660 also has a generally horizontallyoriented rectangular slot 668 into which metal detent pin 592 on section552 of elevation carriage 30 passes. It also has an elongate, arcuateopening 670, through which a bolt 680 passes. The bolt 680 is threadedinto a socket 572 on the elevation carriage, and a spring 682 isinterposed between the head of bolt 680 and retraction bracket 660, asshown in FIGS. 47 and 48. Spring 682 can be selected to provide anychosen amount of force, and tightening or loosening the bolt adjusts theamount of force the spring applies. Accordingly, the force betweenretraction bracket 660 and metal detent pin 592 can be adjusted bytightening or loosening bolt 680. In the depicted embodiment, spring 682has a spring force on the order of 70 to 80 pounds, although othersprings could be used. This serves to bias section 552 of elevationcarriage 30 towards retraction bracket 660, which holds metal detent pin592 in slot 668 until the active injury mitigation system is activatedand the motor and blade are retracted under the table, as will bediscussed later.

Alignment bracket 690, shown in FIGS. 2 and 37 and shown isolated inFIG. 46, is attached to the back of vertical section 302 of trunnion 32via two screws, which pass through holes 692 and 694 in alignmentbracket 690 and holes 332 and 330, respectively, in trunnion 32. Thealignment bracket provides stability and alignment. It helps to keep themotor, arbor, and blade from tilting out of alignment with the trunnion,especially when the blade is tilted for angled cuts and duringretraction of the motor, arbor, and blade. Alignment bracket 690 isformed from a single piece of bent sheet metal, with the top edge 696folded over 90 degrees to one side, and with side edge 698 folded over90 degrees in the same direction to add rigidity. The bottom ofalignment bracket 690 is divided in two unequal portions, and theportion 700, which is closer to the front of the saw, is bent at 90degrees toward the side such that it is parallel with top edge 696 andperpendicular to the main section of the bracket and the side edge 698.The rear portion 702 of the bottom of alignment bracket 690 extends downuntil it is roughly parallel with the top of the hand wheel 34. Foldedsections 696, 698, and 700 add stability to alignment bracket 690, andsection 702 allows elevation carriage 30 to have an increased verticalrange.

In many table saws, the elevation carriage and arbor block are both madefrom die cast aluminum. It can be advantageous to simplify the designand manufacture of a saw by using sheet metal components where possible,which add strength and decrease cost.

In the depicted embodiment, an arbor block assembly comprised of gearbox202, brake cartridge bracket 600, and retraction bracket 660, isdesigned to pivot down to retract the blade and thereby help mitigateinjury in the event a user accidentally contacts the spinning blade. Itis a feature of the depicted embodiment that the arbor block assembly iscomposed of several components. Gearbox 202, which can also be referredto as an arbor block, is made from die cast aluminum, and the brakecartridge and retraction brackets are both made from sheet metal, suchas 2-3 mm thick steel. This decreases the manufacturing cost of the saw,and it increases the strength of arbor block assembly in the areas whereit might deform due to the forces involved in retraction. Motor 200 andgearbox 202 are shown in FIGS. 49 and 50.

A feature of the depicted embodiment is the method by which the motorand gearbox are formed, attached, and suspended in the saw so they tiltand retract with the blade. In the depicted embodiment, the motor andarbor comprise a direct drive system where the motor drives the arbordirectly through gears rather than through a belt. In the depictedembodiment, the arbor and motor are designed to pivot down to retractthe blade and thereby help mitigate injury in the event a useraccidentally contacts the spinning blade. More specifically, table saw10 includes an active injury mitigation system designed to stop andretract the blade in the event of an accident where a person contactsthe spinning blade. The system includes a brake cartridge 630 positionedadjacent the blade, as shown in FIG. 37. Upon detection of contact,brake cartridge 630 will engage and stop the blade to minimize anyinjury, and in doing so, cause the blade to drop or retract until thegearbox contacts a rubber bumper or stop 710 mounted on the trunnion,shown in FIG. 37. The rubber bumper 710 is attached to a metal bumpermount 712, which is in turn attached to sloped bottom section 306 oftrunnion 32 by screws passing through holes in metal bumper mount 712and holes 322 in the trunnion.

In order to simplify the following discussion, arbor block/gearbox 202,with brake cartridge bracket 600 and retraction bracket 660, is referredto collectively as arbor block assembly 2000. In normal use, blade 18,motor 200, and arbor block assembly 2000 are prevented from pivotingdown, or retracting, by the interaction between metal detent pin 592 onelevation carriage 30 and opening 668 in retraction bracket 660.Retraction bracket 660 is attached to elevation carriage 30, andretraction bracket 660 extends partway along the side of arbor block202. Retraction bracket 660 is attached to the arbor block by fourscrews which pass through holes 664 in retraction bracket 660 to threeholes 720 and one hole 722 in arbor block 202 (shown in FIG. 49). In thedepicted embodiment, holes 720 pass all the way through the gearbox,while hole 722 only extends partway through. It will be appreciated byone of ordinary skill in the art that the location and number of screwscould be varied, or other methods of attachment could be used to connectthe retraction bracket to the arbor block.

Metal detent pin 592 on elevation carriage 30 fits into the rectangularslot 668 on the retraction bracket 660, which is in turn bolted togearbox 202. The retraction bracket is a steel plate, approximately 2 to3 mm thick, and is therefore relatively rigid. In normal use, theengagement between retraction bracket 660 and the metal detent pin 592on elevation carriage 30 holds the arbor block assembly and motor inposition and, therefore, holds the blade in position. However, whenbrake cartridge 630 engages and stops the blade, the angular momentum ofthe blade creates a downward force which typically is sufficient to pushmetal detent pin 592 out of rectangular slot 668 by flexing section 552of elevation carriage 30. Arbor block assembly 2000 then pivots downaround an axis defined by shaft 624, which causes the blade to retractbelow the table. In this system, the section 552 of elevation carriage30 acts like a spring and flexes away from the retraction bracket whenmetal detent pin 592 is forced out of rectangular slot 668. Theretraction bracket 660 presses against, and drags across, metal detentpin 592 as the motor, blade, and arbor block assembly pivot down,thereby absorbing some of the energy of the system. As discussed above,section 552 of elevation carriage 30 is additionally biased towards theretraction bracket by spring 682 on bolt 680. When the retractionbracket pivots with the motor assembly and blade, bolt 680 remainsstationary since it is attached to elevation carriage 30, but thearcuate opening 670 on the retraction bracket moves relative to thespring and bolt. Bolt 680 can be adjusted to vary the amount of forcerequired to push metal detent pin 592 out of rectangular slot 668, andto vary the amount of pressure the retraction bracket applies againstmetal detent pin 592 as the arbor block assembly, blade, and motor pivotdown.

After retracting, arbor block assembly 2000 can be reset to its normal,operational position by simply moving the assembly up, either by hand orby the elevation control on the saw, until metal detent pin 592 snapsback into rectangular slot 668.

Brake cartridge bracket 600 is attached to the side of gearbox 202opposite retraction bracket 660 via three screws which thread into theopposite sides of holes 720 and one screw which threads into hole 724.Two oversized pins are pressed into holes 604 in brake cartridge bracket600 and into holes 726 in gearbox 202 to form an interference fit. Holes602 in cartridge mounting bracket 600 require a small amount ofclearance in order for the insertion of the screws into holes 720 and722 in the gearbox 202, since the holes in the cartridge bracket are notthreaded. This could allow cartridge bracket 600 and, therefore,cartridge 630 to move slightly, which is problematic because the spacingbetween the cartridge 630 and the blade 18 is important. Theinterference fit with the pins in holes 604 and 726 serves to minimizeor eliminate motion of cartridge bracket 600 and cartridge 630 relativeto blade 18.

In the depicted embodiment, the end of gearbox 202 near alignmentbracket 690 is supported by an alignment block 714, which is labeled inFIGS. 49, 50, and 55 and is shown isolated in FIGS. 51-53. A threadedhole 730 passes through the alignment block near its rear and is used toattach the alignment block to the gearbox. The rear of the block has agenerally horizontal channel 732 defined by three top projections 736and two bottom projections 738 on the rear of alignment block 714,configured to fit over a corresponding edge 734 on gearbox 202, as shownin FIGS. 54 and 55. The end of gearbox 202 adjacent alignment bracket690 includes two mounting arms 740, each with a through hole, and thebase of the alignment block fits on ledge 734 between mounting arms 740so that the holes in the arms align with the hole 730 near the base ofthe alignment block. A bolt 744 passes through a hole in one of the twoarms 740 on the gearbox, as shown in FIG. 55, and then goes through hole730 in the alignment block and extends through the hole in the other armon the gearbox. A self-locking nut 746, such as a nylon insert lock nut,is then threaded onto the bolt to hold the bolt still. With thisconfiguration, turning bolt 744 causes alignment block 714 to move alongthe bolt, and thereby adjusts the lateral position of the arbor blockand blade relative to the alignment block.

Alignment block 714 includes a vertical notch 750, which isperpendicular to horizontal channel 732 and is configured to fit overthe rear edge of alignment bracket 690. Two arms or projections 722 formnotch 750, and those projections extend over the rear edge of alignmentbracket 690 to prevent the alignment block, arbor block assembly 2000,and motor from moving laterally, and to guide the alignment block as itmoves up and down along the rear edge of alignment bracket 690 whenelevation carriage 30 moves up and down and when the motor, arbor blockassembly 2000, and blade retract.

The clearance between the two projections 722 and alignment bracket 690is chosen to provide enough space so that the alignment block is heldagainst most lateral movement, but not so much that it locks against therear edge of alignment bracket 690 and prevents the motor, arbor blockassembly, and blade from moving up and down. In the depicted embodiment,arbor block assembly 2000 retracts in an arc and, therefore, will movetoward and away from the rear edge of alignment bracket 690 when itretracts and is reset. Retraction of the motor and arbor block assemblycan involve significant forces, so alignment block 714 is made from 30percent glass filled nylon in order to be strong enough to accommodatethe forces involved in retraction.

Power saws such as the lightweight table saw shown at 10 in FIG. 1,hand-held circular saws, track saws, and miter saws typically include amotor that is directly coupled to the blade to drive the blade. Such amotor may be mounted on a moveable arm supported by a base as in thecase of a miter saw, it may include a handle as in the case of ahand-held circular saw or a track saw, or it may be in a cabinet orhousing as in the case of table saw 10 depicted in FIG. 1. FIGS. 49 and50 show a motor 200 with a housing 2004, and FIG. 56 shows some of thecomponents of motor 200. The motor includes a motor armature, as isknown, and the motor armature includes a shaft, such as motor shaft ordrive shaft 2008 shown in FIG. 56. The drive shaft is supported bybearings 2010 and 2012, which in turn are supported by motor housing2004. A fan 2014 is mounted on shaft 2008 to cool the motor. The motoroperates as is known in the art. FIG. 56 shows only selected portions ofmotor 200 for simplicity. For example, the windings that carry electriccurrent to create the force to spin drive shaft 2008 are not shown, andthe stator is not shown. The windings on the motor armature areinsulated from drive shaft 2008, as is known in the art.

Drive shaft 2008 includes a pinion gear 2016 at one end. Pinion gear2016 meshes with a gear 2018, so that when drive shaft 2008 spins piniongear 2016, pinion gear 2016, in turn, drives gear 2018. Gear 2018 ismounted on an arbor shaft 2020 which is supported by bearings 2022 and2023, which, in turn, are supported in gearbox 202. Bearings 2022 and2023 are labeled in FIG. 56, and bearing 2023 is labeled in FIG. 57.Bearing 2023 is supported in a carrier or case 2024, as shown in FIG.61, and case 2024 is then attached to gearbox 202. Bearing 2022 is pressfit into a bearing seat formed in gearbox 202. Blade 18 is held on arbor2020 by collars 2032 and 2034, and by a nut 2036 which threads ontoarbor 2020. Saw 10 is configured so that when drive shaft 2008 andpinion gear 2016 spin, gear 2018 also spins, causing arbor 2020 to spinand drive the blade. Gears 2016 and 2018 can be sized to cause the bladeto spin at a desired speed. In a power saw as described herein, it wouldbe common for an arbor and blade to spin at around 4,000 revolutions perminute. Saws with motors configured as shown in FIG. 56 are oftenreferred to as direct drive saws.

In a direct drive saw equipped with an active injury mitigation systemthat imparts an electrical signal to the blade to detect accidentalcontact with a person, such as table saw 10, the blade must be isolatedfrom electrical ground to maintain the signal on the blade. In theembodiment depicted in FIG. 56, electrical isolation of the blade isaccomplished through gear 2018. In the depicted embodiment, gear 2018 issupported by arbor 2020 and is driven by pinion 2016. The reverse isalso possible; gear 2018 could be on motor shaft 2008, and gear 2018could drive another gear or pinion on arbor 2020.

FIGS. 58, 59, 60 and 61 show arbor 2020 and gear 2018 in more detail,including cross-sectional views in FIGS. 60 and 61. FIG. 60 is takenalong the line A-A in FIG. 59, and FIG. 61 is taken along the line A-Ain FIG. 56. As can be seen, gear 2018 includes an outer ring 2060, whichincludes the teeth of the gear. Outer ring 2060 is made from metal, andspecifically, can be made from powder metal or from a metal such assteel that is forged and cut. A non-conductive inner ring 2062, madefrom plastic, ceramic, or some other non-conductive material, isarranged concentrically along the interior of outer ring 2060. Splinesor keys, such as spline 2063 in FIG. 61, prevent slipping or rotationbetween outer ring 2060 and inner ring 2062. Gear 2018 is formed ormounted on arbor shaft 2020, and arbor 2020 is made from metal. The endof arbor 2020 on which gear 2018 is mounted has keys or splines, such asspline 2065, which prevent slipping or rotation between inner ring 2062and arbor 2020. Inner ring 2062, which is non-conductive, provides thenecessary electrical isolation.

The depicted embodiment of gear 2018 has the advantage of maintainingthe strength of a gear with metal teeth while giving the necessaryelectrical isolation. The non-conductive inner ring is positionedoutward from the axis of rotation of the gear to maximize the surfacearea in contact with outer ring 2060 to minimize shear and to providemore torque. The gear and rings may take many different forms, anddifferent numbers of rings may be used. The present embodiment isadvantageous because the non-conductive inner ring 2062 can be made froma dielectric material such as injection molded plastic to reducemanufacturing costs.

One important consideration is the width of the gap between theconductive arbor shaft 2020 and the conductive exterior ring 2060. Ifthe gap is narrow, capacitance between the metal arbor shaft 2020 andthe motor shaft 2008 can increase, leading to coupling and noise, whichcan interfere with monitoring the signal on the blade and detectingaccidental contact between a user and the blade. It is advantageous tomaximize the amount of dielectric isolation material and minimize thequantity of conductive material without compromising the structuralintegrity of drive gear 2018. As an example, in a power tool with anactive injury mitigation implementation where an electrical signal isimparted to the arbor and blade, noise may come through the gear drivingthe arbor, such as gear 2018 discussed herein. The teeth on the gear arein conductive contact with the motor shaft, and as the teeth mesh, anysignal on the arbor can be perturbed by the movement of the gear teethmoving closer to and then further away from the motor shaft due tocapacitance between the gear teeth and the arbor. Such perturbations canbe called noise, and that noise can be sufficiently big and variable toaffect the ability to detect reliably changes in the signal on the bladethat indicate contact between a person and the blade. Providing asufficient gap of non-conductive material between the arbor and the gearteeth minimizes such noise.

In the depicted embodiment, and at the position of the cross-sectionshown in FIG. 61, the diameter of inner ring 2062 measured from theoutside of one spline 2063 to the outside of the opposite spline is 36.5mm, and the diameter of the inner ring between the splines is 36 mm,making each spline 0.25 mm tall. However, the heights of the splineschange depending on position, as seen in FIG. 58, where the visible,outside surfaces of the splines are higher than in FIG. 61. Outer ring2060 has an internal, annular ridge 2064, shown in FIG. 60, and theheight of the splines under that ridge is less, as shown in FIG. 61.Referring back to FIG. 61, the diameter of arbor 2020 measured from theoutside of one spline 2065 to the outside of the opposite spline is 19mm, while the diameter of the shaft between the splines is 15 mm, makingeach spline 2065 2 mm tall. Of course, splines of different dimensionscan be used, and, as stated, gear 2018 can be sized to achieve thedesired rotational speed of the blade. A common speed of rotation of theblade and arbor in a power saw as described herein is 4,000 revolutionsper minute.

It has been found experimentally that a conductive shaft diameter of15-19 mm, a non-conductive inner ring diameter of 38-46 mm, and an outerring diameter of 52-59 mm provides an optimum balance of strength andelectrical isolation.

The material forming inner ring 2062 can be selected to have acoefficient of thermal expansion similar to the material formingexterior ring 2060 and arbor 2020 to minimize any change of dimensionthat might result in slippage between the shaft, inner ring and exteriorring.

In the depicted embodiment, gear 2018 and arbor 2020 are manufactured asone piece. Arbor 2020 and outer ring 2060 are first formed, such as bymachining or by forming from powder metal, or both. The arbor and outerring are then positioned in a mold, and a non-conductive material isthen injected into the mold between the arbor and the outer ring. Thenon-conductive material molds over the surface of the arbor and fillsthe space between the arbor and the outer ring to form non-conductiveinner ring 2062. At the same time, the non-conductive material formsbearing seats 2066 and 2068 to support bearings 2022 and 2023,respectively. Grooves 2070 can be cut into the end of arbor 2020, asshown in FIG. 60, to increase the contact area between the arbor andbearing seat 2066, thereby minimizing the chance of gear 2018 movingrelative to the arbor.

Motor housing 2004, as shown in FIGS. 49 and 50, can be coated with anelectrically conductive material, such as conductive paint, either onthe inside or outside of the motor housing, or both, to provide a shieldto tend to block electrical noise such as radio frequency interferenceor electromagnetic interference. Due to its size and composition, blade18 can function as an antenna and interfere with the intended functionof the active injury mitigation system. In order to minimize thisproblem, the motor is electrically isolated, or “put in a tin can.” Thestator core of the motor can be grounded to further address this issue.Interference from electrical noise is further minimized through the useof shielded cables. The motor shaft can also be grounded to reducenoise. Grounding a motor shaft and/or an arbor is disclosed in U.S.Provisional Patent Application 62/343,451, filed May 31, 2016, and inPCT Application No. PCT/US17/34566, titled “Detection Systems for PowerTools with Active Injury Mitigation Technology,” filed on May 25, 2017,both of which are incorporated herein by reference. It can be seen inFIG. 49 that two wires 2005 and 2007 extend from the interior of themotor housing. Wire 2005 is used to ground the motor shaft, preferablythrough a conductive coupling as disclosed in the above-identified PCTapplication. Wire 2007 grounds the stator through a simple static ornon-moving connection. Both wires 2005 and 2007 are attached toretraction bracket 660 via a screw passing through hole 672 inretraction bracket 660 (labeled in FIG. 45). These alternatives can beused together to shield or block electrical noise.

FIG. 62 shows a tilt plate 760 installed in table saw 10, and FIG. 63shows tilt plate 760 isolated. Tilt plate 760 attaches to the undersideof table 12 near the front of the saw via two screws, one on the leftside of the front trunnion mounting plate and one on the right side ofthe front trunnion bracket. FIG. 18 shows tilt plate 760 through hole 24in saw housing 22. Tilt plate 760 is formed from a unitary piece of bentsheet metal, shaped generally like a rectangle with a section cut out ofthe middle at the top. A generally horizontally oriented arcuate opening762 is disposed towards the bottom of the tilt plate, through which thetilt lock lever passes, as will be discussed later. Tilt plate 760 alsoincludes a tab 764 to which a ground wire can be connected in order toprovide a reference ground for the saw. Two holes 768 are used to attachstops to tilt plate 760 in order to limit the travel of trunnion 32 to arange of 45 degrees as it tilts. Three screws pass through three holes770 in tilt plate 760 to attach the tilt plate to saw housing 22. Tiltplate 760 is thus held flush with the back side of the front of sawhousing 22.

Below arcuate opening 24 in saw housing 22, there is a second arcuateopening 26, also shown in FIGS. 5 and 18. Elevation control shaft 510passes through arcuate opening 26, as stated previously.

A tilt lock handle 780 is shown in FIGS. 64 and 65. FIG. 65 shows across sectional view of the tilt lock handle 780 and elevation controlshaft bracket 512 along the line F-F—in FIG. 64, with tilt plate 760added. A carriage bolt 794 in tilt lock handle 780 passes through asquare hole 514 near the top of elevation control shaft bracket 512(labeled in FIGS. 35 and 36). A washer 792, a nut (not shown), washer788, spring 786, handle 782, and tilt lock handle cap 784 are thenarranged on bolt 794 as shown in FIG. 65. Tilt plate 760, which is shownin FIG. 65 but not shown in FIG. 64, fits between washer 792 andelevation control shaft bracket 512. Bolt 794 passes through arcuateopening 762 in tilt plate 760, such that the head of bolt 794 andelevation control shaft bracket 512 are behind tilt plate 760, and tiltlock handle 780 is in front of tilt plate 760 and accessible to a user.

In order to tilt the trunnion and accompanying internal saw components,a user would first turn handle 782 to the left (clockwise as seen inFIG. 64) around an axis defined by bolt 794. Since spring 786 serves tobias washer 788, handle 782, and tilt lock handle cap 784 away fromelevation control shaft bracket 512, the clamping force on tilt plate760 would be removed when handle 782 is turned to the left. A user wouldthen use hand wheel 34 and/or tilt lock handle 780 to tilt the trunnionto a desired angle relative to the table, with bolt 794 travelling alongarcuate opening 762 in tilt plate 760 and the accompanying opening 24 insaw housing 22, and elevation control shaft 510 travelling along arcuateopening 26 in saw housing 22. A user would then turn handle 782 to theright (counterclockwise as seen in FIG. 64) around bolt 794 in order toclamp against tilt plate 760 and prevent further movement of thetrunnion and blade.

Between arcuate openings 24 and 26 in saw housing 22, there is anarcuate bevel tilt ruler 800, shown in FIG. 18. A user can use bevelgauge 540 and tilt ruler 800 to ascertain the angle of the trunnion andblade relative to the work surface.

FIGS. 66 through 71 show an alternate exemplary embodiment of the inserthold-down mechanism shown in FIGS. 8 and 9. FIG. 66 shows the top ofinsert 16 with the alternate hold-down mechanism installed therein. Asdisclosed previously, insert 16 includes an indentation 110, slot 20,opening 134, and tabs 112 that contact the underside of the saw table. Afinger lever 1114 is configured to be pulled toward the front of the sawto release the insert from the blade opening. Finger lever 1114 is shownactuated to release the insert (angled up) in FIG. 66, and un-actuatedto secure the insert (generally horizontal) in FIGS. 67 through 70.FIGS. 67 through 70 show the hold-down mechanism isolated from insert16. Finger lever 1114 bends down and becomes a plurality of lock teeth1116, and a dowel portion 1118 is interposed between lever portion 1114and lock teeth 1116. Lock teeth 1116 fit into a plurality of generallyrectangular openings 1122 in a lock block 1120. Lock block 1120 isconnected to the bottom of insert 16 by a screw 1128, which passesthrough a washer 1130 and into a portion of insert 16 which extends downinto an elongated opening 1124 in lock block 1120, as shown in FIGS. 67through 71. The downward extension of insert 16 allows for translationof lock block 1120 in the forward and backward directions, but notsideways or vertically.

When finger lever 1114 is pushed down into indentation 110, lock teeth1116 push lock block 1120 toward the front of the saw, and front edge1126 of said lock block 1120 overlaps with a corresponding ledge ontable 12, as shown in FIG. 71. Lock teeth 1116 engage with rectangularopenings 1122 in lock block 1120 and function like a rack and pin gearto move lock block 1120 forward and backward. The interaction betweenlock teeth 1116 and lock block 1120 can be seen in FIG. 70, which showsa cross section of FIG. 69 along the line A-A in FIG. 69. This preventsthe front of insert 16 from rising up during use. In order to remove theinsert, a user would place a finger into indentation 110 and pull fingerlever 114 up toward the front of the saw. This would cause front edge126 to retract and cease to be in contact with table 12. The user couldthen lift the front of insert 16 out of opening 14, slide tabs 112 outof contact with the table, and remove the insert from opening 14.

The hold-down mechanism depicted in FIGS. 66 through 71 includes a twoposition detent 1132 on each side of lock block 1120. The detents fitinto two indentations 1134 on each side of insert. 16, two of which arelabeled in FIG. 71. The engagement between the detents 1132 on lockblock 1120 and indentations 1134 in insert 16 prevents the hold-downmechanism from moving unexpectedly between the locked and unlockedpositions.

INDUSTRIAL APPLICABILITY

The power saws described herein are applicable to woodworking,manufacturing, packaging, construction, carpentry, material processing,etc. Various disclosed features are particularly relevant to table saws.Various other disclosed features are particularly relevant to tablesaws, hand-held circular saws, track saws, miter saws, and band sawswith active injury mitigation technology.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein. No single feature,function, element or property of the disclosed embodiments is essentialto all of the disclosed inventions. Similarly, where the claims recite“a” or “a first” element or the equivalent thereof, such claims shouldbe understood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements.

It is believed that the following claims particularly point out certaincombinations and subcombinations that are directed to one of thedisclosed inventions and are novel and non-obvious. Inventions embodiedin other combinations and subcombinations of features, functions,elements and/or properties may be claimed through amendment of thepresent claims or presentation of new claims in this or a relatedapplication. Such amended or new claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower or equal in scope to the original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

1. A power tool comprising: a rotatable arbor; a blade mounted on the arbor; a motor to spin the arbor and blade; a detection system to detect when a person contacts the spinning blade; a reaction system triggerable to perform an action to mitigate injury upon detection of the contact; and an electrically isolating gear through which the motor spins the arbor.
 2. The power tool of claim 1, where the electrically isolating gear is on the arbor.
 3. The power tool of claim 1, where the electrically isolating gear includes an outer ring of conductive material and an inner ring of non-conductive material.
 4. The power tool of claim 3, where the inner ring contacts the outer ring, and further comprising splines at the contact between the inner and outer rings.
 5. The power tool of claim 1, where the electrically isolating gear is on the arbor, where the gear includes an outer ring of conductive material and an inner ring of non-conductive material, where the inner ring contacts the arbor, and where the inner ring is formed by molding over the arbor.
 6. The power tool of claim 1, where the electrically isolating gear is on the arbor, where the gear includes an outer ring of conductive material and an inner ring of non-conductive material, where the inner ring includes at least one bearing seat. 